Aircraft environmental control system

ABSTRACT

An environmental control system of an aircraft including a plurality of inlets for receiving a plurality of mediums including a first medium, a second medium, and a third medium and an outlet for delivering a conditioned flow of the second medium to one or more loads of the aircraft. The environmental control system additionally includes a first compressing device and a second compressing device. The second compressing device is arranged in fluid communication with the first compressing device and the outlet. An inlet of the second compressing device is directly connected to an outlet of the first compressing device, and the first compressing device is driven by energy extracted from the first medium. The first medium is a flow of bleed air.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/058,828 filed Jul. 30, 2020, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

Embodiments of the disclosure relate to environmental control systems,and more specifically to an environmental control system of an aircraft.

Aircraft need to have their internal environment controlled. In general,contemporary air conditioning systems are supplied a pressure at cruisethat is approximately 30 psig to 35 psig. The trend in the aerospaceindustry today is towards systems with higher efficiency. One approachto improve efficiency of an aircraft environmental control system is toeliminate the bleed air entirely and use electrical power to compressoutside air. A second approach is to use lower engine pressure. Thethird approach is to use the energy in the cabin outflow air to compressoutside air and bring it into the cabin. Each of these approachesprovides a reduction in airplane fuel burn.

BRIEF DESCRIPTION

According to an embodiment, an environmental control system of anaircraft including a plurality of inlets for receiving a plurality ofmediums including a first medium, a second medium, and a third mediumand an outlet for delivering a conditioned flow of the second medium toone or more loads of the aircraft. The environmental control systemadditionally includes a first compressing device and a secondcompressing device. The second compressing device is arranged in fluidcommunication with the first compressing device and the outlet. An inletof the second compressing device is directly connected to an outlet ofthe first compressing device, and the first compressing device is drivenby energy extracted from the first medium. The first medium is a flow ofbleed air.

In addition to one or more of the features described above, or as analternative, in further embodiments the first compressing device issimultaneously driven by the third medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the first compressing deviceincludes a compressor operably coupled to at least one turbine via ashaft.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine is a dualentry turbine having a first nozzle configured to receive the firstmedium and a second nozzle configured to receive the third medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine includes afirst turbine and a second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium is provided to thefirst turbine and the third medium is provided to the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium and the thirdmedium and mixed downstream from both the first turbine and the secondturbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium and the thirdmedium and mixed downstream from the first turbine and upstream from thesecond turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium is provided to thefirst turbine and the second turbine in series, and the third medium isprovided to the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first turbine and the secondturbine are located at opposite ends of the shaft.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising a ram air circuitincluding a ram air shell having at least one heat exchanger positionedtherein and a dehumidification system arranged in fluid communicationwith the ram air circuit.

In addition to one or more of the features described above, or as analternative, in further embodiments an outlet of the at least oneturbine is arranged in fluid communication with a portion of thedehumidification system.

In addition to one or more of the features described above, or as analternative, in further embodiments an outlet of the at least oneturbine is arranged in fluid communication with the ram air circuit.

In addition to one or more of the features described above, or as analternative, in further embodiments the first compressing deviceincludes a first compressor and the second compressing device includes asecond compressor, the first compressor and the second compressor beingarranged in series relative to a flow of the second medium.

According to an embodiment, an air cycle machine for an environmentalcontrol system for an aircraft, the air cycle machine includes at leastone turbine configured to receive and extract work from a first mediumand a third medium. A compressor is configured to compress a secondmedium and a shaft mechanically couples the at least one turbine and thecompressor. A mixing point is located downstream of at least oneturbine. A mixture of the first medium and the third medium generated atthe mixing point is provided to another component of the environmentalcontrol system.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine includes afirst turbine configured to receive and extract work from the firstmedium and a second turbine configured to receive and extract work fromthe third medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the mixing point is locateddownstream of the first turbine and the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first turbine is positionedadjacent a first end of the shaft and the second turbine is positionedadjacent a second end of the shaft.

In addition to one or more of the features described above, or as analternative, in further embodiments the first turbine is positionedadjacent a first end of the shaft and the compressor is positionedadjacent a second end of the shaft.

In addition to one or more of the features described above, or as analternative, in further embodiments the mixing point is located upstreamof the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first turbine and the secondturbine are arranged in series such that the second turbine is alsoconfigured to receive and extract work from the first medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine includes afirst nozzle for receiving the first medium and a second nozzle forreceiving the third medium.

According to an embodiment, a compressing device for use in anenvironmental control system includes at least one turbine configured toprovide energy by expanding one or more medium. The one or more mediumsprovided at an outlet of the at least one turbine form a heat sinkwithin the environmental control system. A compressor is configured toreceive energy from the one or more mediums expanded across the at leastone turbine. During a first mode of the compressing device, energyderived from a first medium of the one or more mediums is used tocompress a second medium at the compressor and during a second mode ofthe compressing device, energy derived from both the first medium and athird medium of the one or more mediums is used to compress a secondmedium at the compressor.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine includes afirst turbine configured to receive and extract work from the firstmedium and a second turbine configured to receive and extract work fromthe third medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the first turbine and the secondturbine are arranged in series such that the second turbine is alsoconfigured to receive and extract work from the first medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine includes afirst nozzle for receiving the first medium and a second nozzle forreceiving the third medium.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a simplified schematic of a system according to an embodiment;

FIG. 2 is a simplified schematic of a system according to anotherembodiment;

FIG. 3 is a simplified schematic of a system according to anotherembodiment;

FIG. 4 is a simplified schematic of a system according to anotherembodiment;

FIG. 5 is a simplified schematic of a system according to yet anotherembodiment; and

FIG. 6 is a simplified schematic of a system according to yet anotherembodiment

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Embodiments herein provide an environmental control system of anaircraft that mixes mediums from different sources to power theenvironmental control system and to provide cabin pressurization andcooling at a high fuel burn efficiency. The medium can generally be air,while other examples include gases, liquids, fluidized solids, orslurries.

With reference now to FIG. 1, a schematic diagram of a portion of anenvironment control system (ECS) 20, such as an air conditioning unit orpack for example, is depicted according to non-limiting embodiments.Although the environmental control system 20 is described with referenceto an aircraft, alternative applications are also within the scope ofthe disclosure. As shown in the FIGS., the system 20 can receive a firstmedium A1 at a first inlet 22. In embodiments where the environmentalcontrol system 20 is used in an aircraft application, the first mediumA1 may be bleed air, which is pressurized air originating from i.e.being “bled” from, an engine or auxiliary power unit of the aircraft. Itshall be understood that one or more of the temperature, humidity, andpressure of the bleed air can vary based upon the compressor stage andrevolutions per minute of the engine or auxiliary power unit from whichthe air is drawn.

The system 20 is also configured to receive a second medium A2 at aninlet 24 and may provide a conditioned form of at least one of or bothof the first medium A1 and the second medium A2 to a volume 26. In anembodiment, the second medium A2 is fresh air, such as outside air forexample. The outside air can be procured via one or more scoopingmechanisms, such as an impact scoop or a flush scoop for example. Thus,the inlet 24 can be considered a fresh or outside air inlet. In anembodiment, the second medium A2 is ram air drawn from a portion of aram air circuit to be described in more detail below. Generally, thesecond medium A2 described herein is at an ambient pressure equal to anair pressure outside of the aircraft when the aircraft is on the ground,and is between an ambient pressure and a cabin pressure when theaircraft is in flight.

The system 20 may further be configured to receive a third medium A3 atan inlet 28. In one embodiment, the inlet 28 is operably coupled to avolume 26, such as the cabin of an aircraft, and the third medium A3 iscabin discharge air, which is air leaving the volume 26 and that wouldtypically be discharged overboard. In some embodiments, the system 20 isconfigured to extract work from the third medium A3. In this manner, thepressurized air A3 of the volume 26 can be utilized by the system 20 toachieve certain operations.

The environmental control system 20 includes a RAM air circuit 30including a shell or duct, illustrated schematically in broken lines at32, within which one or more heat exchangers are located. The shell 32can receive and direct a medium, such as ram air for example, through aportion of the system 20. The one or more heat exchangers are devicesbuilt for efficient heat transfer from one medium to another. Examplesof the type of heat exchangers that may be used, include, but are notlimited to, double pipe, shell and tube, plate, plate and shell,adiabatic shell, plate fin, pillow plate, and fluid heat exchangers.

The one or more heat exchangers arranged within the shell 32 may bereferred to as ram heat exchangers. In the illustrated, non-limitingembodiment, the ram heat exchangers include a first or primary heatexchanger 34 and a second or secondary heat exchanger 36. However, itshould be understood that a RAM air circuit 30 having any number of ramair heat exchangers, such as a single heat exchanger, or more than twoheat exchangers, is contemplated herein. Within the heat exchangers 34,36, ram air, such as outside air for example, acts as a heat sink tocool a medium passing there through, for example the first medium A1and/or the second medium A2.

The system 20 additionally comprises at least one compressing device. Inthe illustrated, non-limiting embodiments, the system 20 includes afirst compressing device 40 a and a second compressing device 40 b.However, embodiments including only a single compressing device, oralternatively, embodiments including more than two compressing devicesare also within the scope of the disclosure. Further, as shown, at leasta portion of the first compressing device 40 a and the secondcompressing device 40 b may be arranged in series relative to a flow ofa medium, such as the second medium A2 for example, through the system20. The first and second compressing devices 40 a, 40 b may, but neednot have different configurations and components.

In the illustrated, non-limiting embodiment, the compressing devices 40a, 40 b of the system 20 are mechanical devices that include componentsfor performing thermodynamic work on a medium (e.g., extracts work fromor applies work to the first medium A1, the second medium A2, and/or thethird medium A3 by raising and/or lowering pressure and by raisingand/or lowering temperature). Examples of each compressing device 40include an air cycle machine, a two-wheel air cycle machine, athree-wheel air cycle machine, a four-wheel air cycle machine, etc.

In the non-limiting embodiment of FIGS. 1 and 2, the first compressingdevice 40 a is a three-wheel air cycle machine including a compressor 42a and a turbine 44 operably coupled to each other via a shaft 46 a. Thecompressor 42 a is a mechanical device that raises a pressure of amedium and can be driven by another mechanical device (e.g., a motor ora medium via a turbine). Examples of compressor types includecentrifugal, diagonal or mixed-flow, axial-flow, reciprocating, ionicliquid piston, rotary screw, rotary vane, scroll, diaphragm, air bubble,etc. As shown, the compressor 42 a is configured to receive andpressurize the second medium A2. In the illustrated, non-limitingembodiment, the first compressing device additionally includes a powerturbine 48, operably coupled to the compressor 42 a via the shaft 46 a.The turbine 44 a and the power turbine 48 are mechanical devicesoperable to expand a medium and extract work therefrom (also referred toas extracting energy) to drive the compressor 42 a via the shaft 46 a.The first turbine 44 and the power turbine 48 are may be operableindependently or in combination, to drive the compressor 42 a.

In an embodiment, the second compressing device 40 b is also athree-wheel air cycle machine. In the illustrated, non-limitingembodiment, the second compressing device 40 b includes a compressor 42b, a turbine 44 b, and a fan 50 operably coupled to each other via ashaft 46 b. The fan 50 is a mechanical device that can force via push orpull methods a medium (e.g., ram air) through the shell 32 across theone or more ram heat exchangers 34, 36 and at a variable cooling flowrate to control temperatures. Although the fan 50 is illustrated asbeing part of the second compressing device 40 b, in other embodiments,the fan 50 may be separate from the compressing device 40 b, and drivenby another suitable means. In such instances, the fan may beelectrically driven, may be a tip turbine fan, or may be part of asimple cycle machine for example.

The system 20 may additionally include a dehumidification system. In theillustrated, non-limiting embodiment of FIG. 1, the dehumidificationsystem includes a condenser 52 and a water extractor or collector 54arranged downstream from the condenser 52. The condenser 52 and thewater collector 54 are arranged in fluid communication with the flow ofthe second medium A2. The condenser 52 is a particular type of heatexchanger and the water collector 54 is a mechanical device thatperforms a process of removing water from a medium. In the non-limitingembodiment of FIG. 1, the condenser 52 of the dehumidification system isillustrated as a separate heat exchanger located downstream from andarranged in fluid communication with an outlet of the second heatexchanger 36. However, the configuration of the at least onedehumidification system may vary.

In the non-limiting embodiments of FIGS. 2-5, the condenser 52 is formedintegrally with the secondary heat exchanger 36. For example, the secondmedium A2 is configured to flow through a first portion of the heatexchanger that forms the secondary heat exchanger 36, and then through asecond, downstream portion of the heat exchanger, which forms thecondenser 52. In such embodiments, although the entire heat exchanger isarranged within the ram air shell 32, a divider 56 wall may extendparallel to the flow of ram air through the shell 32 at the interfacebetween the first and second portions of the heat exchanger to separatethe ram air shell 32 into a distinct first region 58 and second region59. Accordingly, the fan 50 of the second compressing device 40 b isoperable to draw ram air through the first region 58, across the primaryheat exchanger 34 and the first portion that forms a secondary heatexchanger 36. A fluid flow, distinct from the ram air flow to bedescribed in more detail below, is configured to flow through the secondregion 59, across the second portion of the heat exchanger that formsthe condenser 52. However, it should be understood that embodimentswhere the secondary heat exchanger 36 is arranged within the firstregion 58, and a condenser 52, separate from and arranged in fluidcommunication with an outlet of the secondary heat exchanger 36, isarranged within the second region 59 are also within the scope of thedisclosure.

The elements of the system 20 are connected via valves, tubes, pipes,and the like. Valves (e.g., flow regulation device or mass flow valve)are devices that regulate, direct, and/or control a flow of a medium byopening, closing, or partially obstructing various passageways withinthe tubes, pipes, etc. of the system. Valves can be operated byactuators, such that flow rates of the medium in any portion of thesystem 20 can be regulated to a desired value. For instance, a firstvalve V1 may be configured to control a supply of the first medium A1 tothe system 20, and a second valve V2 may be operable to allow a portionof a medium, such as the first medium A1, to bypass the ram air circuit30. As a result, operation of the second valve V2 may be used to addheat to the system 20 and to drive the compressing device 40 a whenneeded. A third valve V3 may be operable in the event of a pack failure,such as where the system 20 does not have a sufficient flow of thesecond medium A2 to meet the demands of the cabin or other loads. Insuch instances, operation of valve V3 may be used to supplement the flowof second medium A2 with first medium A1, such as at a location upstreamfrom the dehumidification system for example, to meet the demands of theaircraft.

Operation of a fourth valve V4 may be used to allow a portion of thesecond medium A2 to bypass the dehumidification system and the turbine44 b of the second compressing device 40 b and operation of a fifthvalve V5 may be configured to allow a portion of the second medium A2 tobypass the turbine 44 b of the second compressing device 40 b. In anembodiment, a sixth valve V6 is a surge control valve, operable toexhaust a portion of the second medium A2 output from the compressor 42b of the second compressing device 40 b overboard or into the ram aircircuit 30 to prevent a compressor surge. A seventh valve V7 may beconfigured to control a supply of a third medium A3 provided to thepower turbine 48 of the second compressing device 40 b.

With continued reference to FIGS. 1 and 2, the system 20 is operable ina plurality of modes, selectable based on a flight condition of theaircraft. For example, the system 20 may be operable in a first, lowaltitude mode or a second, high altitude mode. The first, low altitudemode is typically used for ground and low altitude flight conditions,such as ground idle, taxi, take-off, and hold conditions, and thesecond, high altitude mode may be used at high altitude cruise, climb,and descent flight conditions.

In the first, low altitude mode, valve V1 is open, and a high pressurefirst medium A1, such as bleed air drawn from an engine or APU, isprovided to the primary heat exchanger 34. Within the first heatexchanger 34, the first medium A1 is cooled via a flow of ram air,driven by the fan 50. As shown in FIG. 1, the cool first medium A1passes sequentially from the first heat exchanger 34 to another heatexchanger 60, where the first medium A1 is further cooled by anothermedium, distinct from the ram air. In other embodiments, best shown inFIG. 2, the heat exchanger 60 may be integrally formed with the primaryheat exchanger 34 and is positioned within the second region 59 of theram air circuit 30.

From the heat exchanger 60, the further cooled first medium A1 isprovided to the inlet of the turbine 44 a of the first compressingdevice 40 a. The high pressure first medium A1 is expanded across theturbine 44 a and work is extracted therefrom. The first medium A1 outputfrom the turbine 44 a has a reduced temperature and pressure relative tothe first medium A1 provided to the inlet of the turbine 44 a. The firstmedium A1 at the outlet of the turbine 44 a may be used to cool thesecond medium A2 within the condenser 52, to be described in more detailbelow, and/or to cool the first medium A1 within the heat exchanger 60.This cooling may occur separately from (FIG. 1) or within the secondregion 59 of the ram air circuit 30 (FIG. 2). After receiving heatwithin heat exchanger 60, the first medium A1 may be exhausted overboardor outside the aircraft. In an embodiment, best shown in FIG. 2, a wallor barrier 61 may be arranged at an upstream end of the second region 59to prevent another medium, separate from the medium output from thefirst compressing device 40 a from passing through the second region 59.Although such a barrier 61 is illustrated in FIG. 2, it should beunderstood that any of the embodiments of the ram air system including aseparate first and second region 58, 59 may include such a barrier 61.

The work extracted from the first medium A1 in the turbine 44 a, drivesthe compressor 42 a, which is used to compress a second medium A2provided from an aircraft inlet 24. As shown, the second medium A2, suchas fresh air for example, is drawn from an upstream end of the ram aircircuit 30 or from another source, and provided to an inlet of thecompressor 42 a. The act of compressing the second medium A2, heats thesecond medium A2 and increases the pressure of the second medium A2. Inan embodiment, a configuration of the compressor 42 a is selected toincrease the pressure of the second medium A2 to less than double itsstarting pressure.

During normal operation, the second medium A2 output from the compressor42 a of the first compressing device 40 a is provided to the compressor42 b of the second compressing device 40 b. Within the compressor 42 b,the second medium A2 is further heated and pressurized. Accordingly, thesecond medium A2 is configured to flow through the compressor 42 a ofthe first compressing device 40 a and the compressor 42 b of the secondcompressing device 40 b in series.

In some embodiments, the compressed second medium A2 output from thecompressor 42 b is provided to an ozone removal heat exchanger 62,before being provided to the secondary heat exchanger 36 where it iscooled by ram air. In the illustrated, non-limiting embodiment, thefirst medium A1 and the second medium A2 are configured to flow throughthe primary and second heat exchangers 34, 36, respectively, in the samedirection relative to the ram air flow. However, embodiments where thefirst and second mediums A1, A2 flow in different directions are alsowithin the scope of the disclosure.

The second medium A2 exiting the secondary heat exchanger 36 is thenprovided to the condenser 52, where the second medium A2 is furthercooled by the first medium A1 output from the turbine 44 a of the firstcompressing device 40 a. From the condenser 52, the second medium A2 isprovided to the water collector 54 where any free moisture is removed,to produce cool medium pressure air. This cool pressurized second mediumA2 then enters the turbine 44 b where work is extracted from the secondmedium A2 and used to drive the compressor 42 b and the fan 50. Thesecond medium A2 output from the turbine 44 b is then sent to one ormore loads of the aircraft, such as to condition the volume or chamber26.

The high altitude mode of operation is similar to the low altitude modeof operation. However, in some embodiments, valve V2 may be open toallow at least a portion of the first medium A1 to bypass the primaryheat exchanger 34 and heat exchanger 60. Valve V2 may be operated tocontrol, and in some embodiments, maximize, the temperature of the firstmedium A1 provided to the turbine 44 a of the first compressing device40 a. In an embodiment, the pressure ratio across the turbine is lessthan a conventional turbine. As a result, the work extracted from thefirst medium A1 within the turbine 44 a may be optimized whileexhausting the first medium A1 therefrom with a temperature suitable tofunction as a heat sink with respect to the condenser 52 and/or heatexchanger 60.

In the high altitude mode of operation, the compressor 42 a of the firstcompressing device 40 a may be operable to increase the pressure of thesecond medium A2 up to four times its initial pressure. Although notshown, in an embodiment, the second medium A2 may be cooled between theoutlet of the compressor 42 a of the first compressing device 40 a andthe inlet of the compressor 42 b of the second compressing device 40 b,such as within an outflow heat exchanger. In such embodiments, thesecond medium A2 may be cooled via any suitable medium, including, butnot limited to the third medium A3 for example.

In the illustrated, non-limiting embodiment, the third medium A3provided to the system 20 via inlet 28 is delivered to the power turbine48 of the first compressing device 40 a. The additional work extractedfrom the third medium A3 within the power turbine 48, is used incombination with the work extracted from the first medium A1, to drivethe compressor 42 a. As shown, the third medium A3 may be mixed with thefirst medium A1 at a mixing point MP1. In the illustrated, non-limitingembodiment, the mixing point MP1 is located downstream from an outlet ofthe turbine 44 a and from the power turbine 48. However, embodimentswhere the mixing point MP1 is arranged directly at the outlet of theturbine 44 a, are also within the scope of the disclosure. In the highaltitude mode of operation, this mixture of first medium and thirdmedium A1+A3 may be used to cool the second medium A2 within thecondenser 52, and/or to cool the first medium A1 within the heatexchanger 60.

The second medium A2 output from the compressor 42 a of the firstcompressing device 40 a and/or the compressor 42 b of the secondcompressing device 40 b may be configured to follow the same flow pathwith respect to the secondary heat exchanger 36 and condenser 52 aspreviously described for the low altitude mode of operation. In anembodiment, valve V5 is open in the high altitude mode. As a result, atleast a portion of the second medium A2 output from the condenser 52bypasses the water collector 54 and the turbine 44 b of the secondcompressing device 40 b.

Depending on the temperature and humidity conditions of the day, thesecond medium output from the condenser 52 may be too cold to providedirectly to the cabin or chamber 26, via valve V5. In such instances,during the high altitude mode of operation, valve V4 may also be opened,thereby allowing a portion of the heated second medium A2 output fromeither the compressor 42 a or the compressor 42 b to mix with the coldsecond medium A2 upstream from an outlet of the system 20. Accordingly,valve V4 can be controlled to achieve a second medium A2 having adesired temperature for conditioning the cabin 26.

With reference now to FIG. 3, another configuration of the system 20 isillustrated. The system 20 is similar to the configuration of FIG. 2;however, in the illustrated, non-limiting embodiment, the compressor 42a is arranged at an end of the shaft 46 a, the turbine 44 a is arrangedat an opposite end of the shaft, closes to the ram air circuit 30, andthe power turbine is arranged between the compressor 42 a and theturbine 44 a. This is different from the configuration of FIGS. 1 and 2,where the compressor 42 a was mounted at a center of the shaft 46 a,between the turbine 44 a, and the power turbine 48. In the embodimentillustrated in FIG. 3, the mixing point MP2 of the third medium A3output from the power turbine 48 and the first medium A1 output from theturbine 44 a may be arranged at or downstream from the outlet of theturbine 44 a.

Yet another configuration of the system 20 is illustrated in thenon-limiting embodiment of FIG. 4. As shown, the system 20 issubstantially similar to the configuration of the system illustrated anddescribed with respect to FIG. 3; however, the compressing device 40 aincludes a bleed turbine 70 in place of the power turbine 48.Accordingly, during both the low altitude and high altitude modes ofoperation, the first medium A1 is provided to the bleed turbine 70 andthen to the turbine 44 a sequentially. The work extracted from the firstmedium A1 in both turbines 70, 44 a is used to drive the compressor.Further, the first medium A1 output from the first turbine 44 a is usedto cool the flows of medium within the condenser 52 and/or the heatexchanger 60. As previously described, in a high altitude mode ofoperation, the third medium A3 is additionally provided to the system 20and work is extracted therefrom. As shown, the third medium A3 is mixedat a mixing point MP3 with the first medium A1. In the illustrated,non-limiting embodiment, the mixing point MP3 is located downstream froman outlet of the bleed turbine 70 and upstream from an inlet of thefirst turbine 44 a. By mixing the plurality of mediums within the aircycle machine, the complexity of the housing of the compressing device40 a is reduced since only a single outlet for both the first medium andthe third medium is formed therein.

In an embodiment, the pressure ratio of one or more of the turbines ofthe first compressing device 40 a is reduced relative to existingturbines. As used herein, the term “pressure ratio” is intended todescribe the ratio of the pressure of the medium provided to an inlet ofthe turbine and the pressure of the medium provided at the outlet of theturbine. In an embodiment, such as embodiments of the system 20including a plurality of turbines 44 a, 70 arranged in series relativeto a flow of one or more mediums, the pressure ratio of each of theturbines may be reduced compared to conventional turbines. By using aplurality of turbines having a reduced pressure ratio in series, theenergy extracted from the medium within the turbines may be maximized.

With reference now to FIG. 5, the first compressing device 40 a of thesystem 20 is a two-wheel air cycle machine. In the illustrated,non-limiting embodiment, the first compressing device 40 a includes acompressor 42 a and the turbine 44 a is a dual entry turbine. The dualentry turbine is configured to receive a plurality of flows, such as ofdifferent mediums for example. A dual entry turbine typically hasmultiple nozzles, each of which is configured to receive a distinct flowof medium at a different entry point, such that multiple flows can bereceived simultaneously. For example, the turbine can include aplurality of inlet flow paths, such as an inner flow path and an outerflow path, to enable mixing of the medium flows at the exit of theturbine. The inner flow path can be a first diameter, and the outer flowpath can be a second diameter. Further, the inner flow path can alignwith one of the first or second nozzles, and the outer flow path canalign with the other of the first or second nozzles.

In an embodiment, one of the inlets or nozzles of the dual entry turbineis arranged in fluid communication with the flow path of the firstmedium A1, such as downstream from an outlet of the heat exchanger 60for example. Accordingly, during both the first inlet of the dual entryturbine. The work extracted from the first medium A1 in the dual entryturbine is used to drive the compressor 42 a. As previously described,in a high altitude mode of operation, the third medium A3 isadditionally provided to the system 20 and work is extracted therefrom.As shown, the third medium A3 may be provided to a second inlet ornozzle of the dual entry turbine. In such embodiments, the mixing pointMP4 of the third medium A3 and the first medium A1 can be at the dualentry turbine, such as at an outlet of the turbine for example, oralternatively, may be downstream therefrom.

With reference now to FIG. 6, in another embodiment, the compressingdevice 40 a includes a dual entry turbine 70 in addition to turbine 44a. As shown, one of the inlets or nozzles of the dual entry turbine 70is arranged downstream from and in series with an outlet the turbine 44a. Accordingly, during both the low altitude and high altitude modes ofoperation, the first medium A1 is provided to turbine 44 a then to thedual entry turbine 70 sequentially. The work extracted from the firstmedium A1 in both the turbine 44 a and the dual entry turbine 70 is usedto drive the compressor 42 a. Further, the first medium A1 output fromthe dual entry turbine 70 is used to cool the flows of medium within thecondenser 52 and/or the heat exchanger 60. As previously described, in ahigh altitude mode of operation, the third medium A3 is additionallyprovided to the system 20 and work is extracted therefrom. As shown, thethird medium A3 may be provided to a second inlet or nozzle of the dualentry turbine 70. In such embodiments, the mixing point MP of the thirdmedium A3 and the first medium A1 is located at the dual entry turbine70, such as at an outlet of the turbine 70 for example, oralternatively, may be downstream therefrom.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. An environmental control system of an aircraftcomprising: a plurality of inlets for receiving a plurality of mediumsincluding a first medium, a second medium, and a third medium; an outletfor delivering a conditioned flow of the second medium to one or moreloads of the aircraft; a first compressing device and a secondcompressing device, the second compressing device being arranged influid communication with the first compressing device and the outlet,wherein an inlet of the second compressing device is directly connectedto an outlet of the first compressing device, and the first compressingdevice is driven by energy extracted from the first medium, wherein thefirst medium is a flow of bleed air.
 2. The environmental control systemof claim 1, wherein the first compressing device is simultaneouslydriven by the third medium.
 3. The environmental control system of claim1, wherein the first compressing device includes a compressor operablycoupled to at least one turbine via a shaft.
 4. The environmentalcontrol system of claim 1, wherein the at least one turbine is a dualentry turbine having a first nozzle configured to receive the firstmedium and a second nozzle configured to receive the third medium. 5.The environmental control system of claim 1, wherein the at least oneturbine includes a first turbine and a second turbine.
 6. Theenvironmental control system of claim 5, wherein the first medium isprovided to the first turbine and the third medium is provided to thesecond turbine.
 7. The environmental control system of claim 5, whereinthe first medium and the third medium and mixed downstream from both thefirst turbine and the second turbine.
 8. The environmental controlsystem of claim 5, wherein the first medium and the third medium andmixed downstream from the first turbine and upstream from the secondturbine.
 9. The environmental control system of claim 8, wherein thefirst medium is provided to the first turbine and the second turbine inseries, and the third medium is provided to the second turbine.
 10. Theenvironmental control system of claim 5, wherein the first turbine andthe second turbine are located at opposite ends of the shaft.
 11. Theenvironmental control system of claim 5, further comprising a ram aircircuit including a ram air shell having at least one heat exchangerpositioned therein; a dehumidification system arranged in fluidcommunication with the ram air circuit.
 12. The environmental controlsystem of claim 11, wherein an outlet of the at least one turbine isarranged in fluid communication with a portion of the dehumidificationsystem.
 13. The environmental control system of claim 12, wherein anoutlet of the at least one turbine is arranged in fluid communicationwith the ram air circuit.
 14. The environmental control system of claim1, wherein the first compressing device includes a first compressor andthe second compressing device includes a second compressor, the firstcompressor and the second compressor being arranged in series relativeto a flow of the second medium.